1. Field of the Invention
The present invention relates to a sensor, and more particularly to a mounting structure for a sensor that measures the running state of an industrial vehicle, such as a fork-lift truck.
2. Description of the Prior Art
Prior art fork-lift trucks have tiltable axles for improving riding quality and running stability. However, when a load on the fork is relatively heavy, when the vertical position of the load on the fork is relatively high, or when the fork-lift truck makes a high speed turn, the running stability of the fork-lift truck is decreased due to tilting motion of the axle. An apparatus for locking the axle to prevent the tilting motion of the axle relative to the body frame in these situations has been proposed. The apparatus includes a sensor for measuring the yaw rate or lateral acceleration (centrifugal force) of the vehicle. The apparatus further includes a lock mechanism for locking the tilting motion of the axle when the yaw rate or the lateral acceleration exceeds a predetermined value.
For example, the yaw rate sensor utilizes a piezoelectric vibrational gyroscope or a fiber-optic gyroscope. When the measured yaw rate or the lateral acceleration, which is calculated based on the measured yaw rate and the speed of the fork-lift truck, exceeds a predetermined value, the lock mechanism will be activated. The lock mechanism has dampers that are arranged between the body frame and the axle. When the dampers are locked, tilting of the axle is prohibited. As a result, the vehicle is stabilized.
In general, accuracy of the sensor is affected by the way the sensor is mounted. If the sensor is improperly mounted on the vehicle, the accuracy of the sensor will be low. In the case of a yaw rate sensor having a gyroscope, the axis of the gyroscope must be parallel to the vehicle""s turning axis, which is vertical. That is, the axis of the sensor should be vertically fixed on the vehicle. In a case of the acceleration sensor, the direction of the acceleration to be measured should be parallel to the moving direction of the vehicle.
However, it is sometimes difficult to provide enough space for mounting the sensor, so the sensor is not always properly mounted. Moreover, typically, such sensors are not water-proof and dust-proof. Therefore, the additional space required for a water and dust proof structure would further limit the available mounting space.
One way to mount the sensor on the vehicle is to mount the sensor directly on the vehicle body. In this proposal, the sensor is covered by a water and dust proof cover, and a control unit is accommodated in a water and dust proof metal case. The control unit has an electric circuit for controlling the tilting motion of the axle. The sensor, which is mounted on the vehicle body, is electrically connected to the control unit, which is separated from the sensor, with a wire harness.
In this proposal, the sensor unit is relatively small, so that the attitude and position of the sensor unit on the vehicle are not substantially restricted. Therefore, the sensor can be mounted on the vehicle even if the mounting space is small. Furthermore, the axis of the sensor can be vertically fixed. However, since the harness that connects the sensor and the control unit is positioned outside of the cases, the harness is easily cut, so the electrical connection is unreliable.
Another way to mount the sensor on the vehicle is to put both the sensor and the control unit in a common case. In this instance, as shown in FIG. 6, a circuit board 41, which has an electric circuit on it, is housed in the case 40 of the control unit. The sensor 42 is directly mounted on the board 41. A terminal 43 is provided on the sensor 42. The terminal 43 is soldered to an electrode (not shown) of the board 41. The sensor 42 is thus electrically connected to the control unit.
In this instance, the sensor 42 is directly mounted on the board 41, so the electrical connection is not exposed. However, the case 40 is relatively large, so the attitude and the location of the sensor 42 on the vehicle is restricted. Therefore, the operational axis of the sensor 42 may not be perfectly vertical when the sensor 42 is mounted on the vehicle.
Furthermore, the sensor 42 is relatively heavy in comparison with other circuitry parts, so the solder, which connects the terminal 43 and the electrode of the board, is susceptible to breakage due to vibrations.
An objective of the present invention is to provide an improved support assembly for a sensor that measures a running state of a vehicle.
Another objective of the present invention is to provide a sensor support assembly that achieves a more reliable electrical connection between the sensor and a circuit board.
Another objective is to provide a sensor support assembly that uses existing parts, thus reducing costs.
For achieving the objectives of the present invention, an assembly is provided for mounting a sensor that measures a running state of a vehicle on the vehicle. The sensor is mounted with a predetermined orientation. The assembly includes a control unit for controlling the vehicle based on a measured signal transmitted from the sensor. The control unit includes a circuit board. The assembly further includes a case to be fixed to the vehicle for housing the circuit board and a holding member for holding the sensor at an angle relative to the circuit board. The holding member maintains the orientation of the sensor with respect to the vehicle when the case is fixed to the vehicle.
Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.